1. Field of the Invention
The present invention relates to an image forming apparatus, such as a copier, a facsimile, or a printer, that emits light in a main scanning direction intersecting a direction, in which the surface of a latent image carrier moves, to write a latent image onto the latent image carrier.
2. Description of the Related Art
This type of image forming apparatus according to the related art has a problem in that irregularity in image density (hereinafter, referred to as “the deviation of image density”) occurs in the main scanning direction in which scanning is performed with light. The deviation of image density in the main scanning direction occurs, for example, when there is a deviation in the emission intensity of light in the main scanning direction. When there is a deviation in the emission intensity of light in the main scanning direction, the deviation of image density in the main scanning direction occurs in the finally obtained image. For example, in an exposure process, a light beam from a light source in an optical scanning device is emitted in the main scanning direction by a deflector, is guided by an optical element, and is then emitted from the optical scanning device to the surface of a photosensitive drum, which is a carrier. In this case, the deviation of the emission intensity of light in the main scanning direction occurs due to, within the scanning range of light emitted in the main scanning direction, a difference in the incident angle of light on the deflection surface of the deflector or a spatial variation in the reflectance or transmittance of the optical element through which the deflected light passes.
In order to solve the problem of the deviation of the emission intensity of light in the main scanning direction, an image forming apparatus has been proposed which corrects the deviation of the emission intensity of light in the main scanning direction such that a light emission intensity distribution (hereinafter, referred to as a “light intensity distribution”) in the main scanning direction becomes uniform or an intended light intensity distribution is obtained (see Japanese Patent Application Laid-open No. 2004-029217, Japanese Patent Application Laid-open No. 2006-234862, and Japanese Patent Application Laid-open No. 2009-0986261). In the image forming apparatus, for example, in the factory, the light intensity distribution of the optical scanning device in the main scanning direction is measured in advance and correction profile data that allows the light intensity distribution to be uniform or an intended light intensity distribution to be obtained is created. The correction profile data is stored in a memory provided in the image forming apparatus and is reflected to the output intensity of light from the optical scanning device. In this way, it is possible to reduce the deviation of image density in the main scanning direction due to the deviation of the emission intensity of light in the main scanning direction.
However, the image forming apparatus according to the related art has a problem in that it is difficult to arbitrarily adjust the deviation of image density in the main scanning direction. For example, in the image forming apparatus disclosed in Japanese Patent Application Laid-open No. 2006-234862, the light intensity distribution in the main scanning direction is adjusted so as to prevent the deviation of image density in the main scanning direction due to the deviation of the emission intensity of light in the main scanning direction. When the adjustment is performed, the capability to form an image is adjusted on the basis of the detection result of the amount of toner adhering in a reference toner image which is formed on the latent image carrier before the latent image of an output image is formed. In the image forming apparatus, it is possible to prevent a deficiency or excess of the toner density of the entire output image due to the adjustment of the light intensity distribution, but it is difficult to arbitrarily adjust the deviation of image density in the main scanning direction.